The present invention relates a passenger airbag, which is filled with gas during an emergency situation such as, for example, a frontal or side impact.
Current airbag cushion designs may include multiple chambers and may incorporate an inter-chamber venting system that allows gas to flow from one chamber to another. These cushions are configured to rapidly contact a vehicle occupant when inflated, to limit movement of the passenger head, neck and thoracic regions. However, these cushion designs do not differentiate between these different regions with regard to the stiffness or resistance of the various portions of the airbag to contact with each region.
Research has shown that the masses of the various body portions contacting an airbag differ greatly. For example, the mass ratio of the Thorax to Head & Neck regions may range from between 5:1 to 8:1, depending on the sex of the individual. Due to the differences in body part masses and the dynamics of contact between the occupant and the cushion, it has proven difficult to design a multi-chamber airbag which provides optimum protection for each portion of the body contacting the airbag.
An additional challenge involves the use of a dual stage inflator. A dual stage inflator is typically employed to provide sequential production of gas depending on crash severity and depending on occupant size and/or position for example. A dual stage inflator may be defined as containing two combustion chambers, a primary and a secondary chamber, with each chamber when operated providing a first and second stage of combustion. In general, the primary chamber is configured to ignite and produce gases in the event of a crash event. The secondary chamber is provided to affect a greater restraint due to greater gas production should the occupant be recognized as being of greater weight and size, and/or, should the impending crash severity be calculated as requiring a greater or faster restraint. Although effective in these regards, a dual stage inflator is relatively more expensive than a single stage inflator or one that only includes a single combustion chamber with one stage of combustion. It would therefore be an improvement in the art to provide a solution that mitigates the need for a dual stage inflator but still affords the protection provided by a dual stage inflator.
Thus, a need exists for an airbag design which permits the stiffness or resistance to occupant impact provided by each portion of the airbag to be adjusted according to the time elapsed from the initiation of airbag deployment, the size of the occupant, and/or the masses of different portions of the occupant's body contacting an associated portion of the airbag.